Address observatory analysis issues.

runtime/observatory/tests/service/async_single_step_into_test.dart

Index: runtime/observatory/tests/service/async_single_step_into_test.dart
diff --git a/runtime/observatory/tests/service/async_single_step_into_test.dart b/runtime/observatory/tests/service/async_single_step_into_test.dart
index 129ff6a0fc4b5a57d763e49fbb28ce59d4e4f9d2..04b0875b2efcf0741ccfc65c2db78837ed266fd5 100644
--- a/runtime/observatory/tests/service/async_single_step_into_test.dart
+++ b/runtime/observatory/tests/service/async_single_step_into_test.dart
@@ -4,16 +4,14 @@
 // VMOptions=--error_on_bad_type --error_on_bad_override  --verbose_debug --async_debugger
 
 import 'dart:developer';
-import 'package:observatory/models.dart' as M;
-import 'package:observatory/service_io.dart';
-import 'package:unittest/unittest.dart';
+
 import 'service_test_common.dart';
 import 'test_helper.dart';
 
-const LINE_A = 19;
-const LINE_B = 20;
-const LINE_C = 25;
-const LINE_D = 26;
+const LINE_A = 17;
+const LINE_B = 18;
+const LINE_C = 23;
+const LINE_D = 24;
 
 helper() async {
   print('helper'); // LINE_A.